Projectors are widely used in many circumstances. Recently, with increasing development of science and technology, a pico projector (also referred as a micro display) has been introduced into the market. The pico projector is designed to have small size and light weightiness. Generally, the pico projector is embedded into a portable electronic device (e.g. a mobile phone or a personal digital assistant), so that the pico projector may be directly utilized. Alternatively, the pico projector is separated from the portable electronic device, and thus the pico projector may be operated after the pico projector is in communication with the portable electronic device. By means of the pico projector, a corresponding projection image may be projected on a flat projection surface to be viewed by the user. In such way, the image to be shown may be projected in a maneuverable and real-time manner.
Generally, the pico projector uses light sources to emit light beams, and projects the light beams on the projection surface through a projection module. In a conventional pico projector, the projection module is for example an LCoS (liquid crystal on silicon) panel, a reflective LCD (liquid crystal display) panel, a DMD (digital Micro-mirror device) or a micro scanning mirror (i.e. according to a MEMS technology). Before the light beams are projected out through the projection module, the light beams are homogenized, focused or shaped by associated optical elements of the pico projector. After the light beams are homogenized, focused or shaped, the adjusted light beams are projected out. Generally, the light sources used in the pico projector are for example LED light sources or laser light sources.
FIG. 1 is a schematic planar view illustrating a portion of a conventional pico projector. As shown in FIG. 1, the conventional pico projector 1 comprises three primary color light sources 11, 12 and 13. For example, the color light source 11 is a red light source, the color light source 12 is a green light source, and the color light source 13 is a blue light source. The three primary color light sources 11, 12 and 13 are laser light sources. The pico projector 1 further comprises three collimator lenses 110, 120 and 130 corresponding to the three primary color light sources 11, 12 and 13, respectively. The color light beams from the three primary color light sources 11, 12 and 13 are adjusted by the collimator lenses 110, 120 and 130. The pico projector 1 further comprises two dichroic mirrors 141 and 142. The color light beams from the three primary color light sources 11, 12 and 13 are selectively transmitted through or reflected by the dichroic mirrors 141 and 142, so that the three color light beams are mixed with each other. Afterwards, the mixed light beam is converted into a scanning line by a scanning mirror 15. The scanning line is swept across projection surface along a horizontal axis and a vertical axis in order to produce a planar image on the projection surface.
For assembling the conventional pico projector 1, the color light sources 11, 12 and 13 and the scanning mirror 15 are firstly fixed on predetermined position, and then the three collimator lenses 110, 120 and 130 are fixed on positions corresponding to the color light sources 11, 12 and 13. For achieving an optimal projecting performance, the positions of three collimator lenses 110, 120 and 130 should be elaborately determined to adjust the angles of the color light beams and mix the color light beams. For example, after UV curing adhesives are coated on the predetermined positions of the three collimator lenses 110, 120 and 130, the three collimator lenses 110, 120 and 130 are placed on the predetermined positions, and then the UV curing adhesives are exposed to UV light. After the UV curing adhesives are solidified, the three collimator lenses 110, 120 and 130 are securely fixed on the predetermined positions.
However, the conventional pico projector still has some drawbacks. For example, specified spaces should be retained at the positions near the collimator lenses 110, 120 and 130. These spaces are open to each other and in communication with each other in order for the manufacturer to assemble, install or adjust the collimator lenses 110, 120 and 130. That is, these collimator lenses 110, 120 and 130 are not separated from each other in the space. Moreover, the scanning mirror 15 or other optical elements are all in these spaces which are in communication with each other.
During the process of dispensing adhesives, some drawbacks may occur. Before the adhesives are solidified, the adhesives have flowability. Once the adhesives flow to other components, these components are adversely affected. Moreover, when the color light beams from the color light sources 11, 12 and 13 are directed to these open spaces, the scattering phenomenon or the diffusion phenomenon of the color light beams may be interfered with each other. Under this circumstance, the projection image contains obvious stray light.